An ADC's accuracy is largely limited by the ADC's front end. One technique for an ADC front end is to use an operational amplifier where the voltage to be converted by the ADC is fed to an input resistor connected for example to the negative input of the operational amplifier, the positive input of the operational amplifier is connected to ground, the output of the operational amplifier is coupled through a feedback resistor to the negative input of the operational amplifier. This configuration establishes the gain of the ADC's front end. The output of the operational amplifier is then coupled to a switch. The switch when closed connects to a sampling capacitor. The sampling capacitor serves as the input to the ADC conversion circuitry. Noise in the ADC's front end introduces errors. Non-linearities in the ADC's front end introduces errors. Sampling errors introduce errors. This presents a technical problem for which a technical solution using a technical means is needed.